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Our
survey customers often ask us about how they should perform diesel
maintenance. This is a very easy question to answer.
We've yet to see a diesel
manufacturer that did not produce an excellent manual. They also
provide a book-size parts manual. If you read and follow the one,
you should have little use for the other. Diesel manuals contain
every bit of information you need to know about how to maintain
your engines, and more. What follows is a general discussion of
what you should do and why you should do it.
One of the reasons why
people often do not follow these instructions is because the frequency
of recommended maintenance is a little bit more than the boat owner
bargained for in terms of time and cost. In fact, our experience
is that 80% of all the engines we see, in terms of the maintenance
condition, come nowhere close to what the manuals recommend.
There are two fundamental
points to diesel maintenance:
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Lubrication system
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Cooling System
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| This is what happens to
pistons after an overheat. The piston is distorted and the
rings are stuck, frozen into the ring grooves. This then caused
blow-by into the crankcase. |
High exhaust emissions
into the crankcase then caused an acid build up in the lube
oil that resulted in this bearing erosion. Eventually this
will result in bearing failure. The root cause, however, was
lack of cooling system maintenance. |
Lubrication
Few people are unaware that diesel lube oil must be changed
frequently, 100 hours is the usual interval. Why so often? It's
because large amounts of carbon is a by-product that ends up in
the oil. If allowed to build up and remain in the oil, the lubricating
ability of the oil is severely retarded. Moreover, carbon blocks
heat transfer and retards the cooling function of the oil as well.
Engine oil will also suffer a build up of sulfuric acid, which can
damage bearings as shown above.
Equally important is
good filters. Believe me, only the very best and most expensive
oil filters are good enough to be significantly effective. I recommend
that you buy either OEM or top name brand filters regardless of
cost.
Don't cheat on your
lube oils, either. The manufacturers are not blowing smoke, so just
follow the recommendation for oil grades. They know better than
your buddy down the dock who may have other ideas that he heard
from yet someone else.
The Vast Majority
of All Diesel Damage is Due to Lack of Cooling System Maintenance
We don't know the exact percentage of engine failures
that result from lack of cooling system maintenance, but it is surely
at least 50%. You need to understand this: Diesel engines operate
under a piston compression of around 350 to 550 psi. That is three
to four times the amount of a gas engine. This high compression
puts great strain on the engine and can build up heat very rapidly
(like within 60 seconds) if there is a failure in the cooling system.
Diesel cooling systems are vastly more critical than gas engine
cooling systems. Gas engines can suffer from numerous moderate overheats
without causing catastrophic damage. THIS IS NOT TRUE OF DIESELS.
Diesel engines can and will suffer serious damage even as the result
of relatively minor overheat conditions. This is because the overheating
occurs so rapidly, and because the internal parts are less tolerant
of damage than a gas engine.
Most overheats occur
because the engines are never inspected and leaks are never found
and repaired. Cooling system hoses are allowed to age, and they
eventually burst, leak or blow off.
Another common cause
is failure to keep the cooling system clean. Instead of adding a
properly mixed solution of recommended coolant, owners just pour
water in, or add straight coolant. Proper ratios of engine coolant
are critical to proper cooling and the prevention of corrosion.
System Gasketing
Due to vibration and age, system gaskets do not last forever
and will inevitably start to leak. The leaks usually occur in a
location that is not easily seen. Thus coolant is lost and the engine
overheats. Consider this: Can you take a guess at how often anyone
ever checks the engine coolant before starting the engines when
we do a sea trial? The incredible answer is that not only do boat
owners not check the coolant, they don't check the oil either. These
very confidant souls who are going to eventually pay the price for
their carelessness.
Do Your Engines
Vibrate? If your engines or any part thereof vibrate to
the point where it looks blurry, or you can see it shaking, rest
absolutely assured that that vibration is capable of destroying
your engine. First of all, it's going to break all of the gasket
surfaces loose. Or hoses will go loose. And then the engine is going
to start leaking fluids. If the engines are vibrating excessively,
you need to have the problem diagnosed and get the vibration stopped.
Engine Alarms
You should regard your alarm systems like light bulbs in
your house. They will operate for a short period of time and then
crap out. They are a constant maintenance thing, and the failure
to maintain them could be one of the costliest mistakes you'll ever
make.
Exhaust Temperature
Alarms One of the weaknesses of water temperature
alarms is that they will not function when there is a complete loss
of cooling water around the sensor. The sensor only works when it
is immersed in water. For this reason, I strongly recommend
that you have exhaust temperature alarms installed. These will function
when the others won't. The cost of having them installed is minimal,
and a drop in the bucket compared to the cost of an overheat.
When to Inspect
Engine coolant should be checked every time before starting the
engine. That does not mean looking at the coolant recovery tank.
You should NEVER use the recovery tank as an indication of coolant
level in the engine. Half the time these things do not work properly.
The first sign of leaking
gaskets does not mean that you should replace THAT gasket. it means
you should replace all such gaskets. If one is starting to leak,
soon they all will.
Coolers All
diesel will have at least three coolers: the heat exchanger, oil
and fuel cooler -- and most likely a transmission cooler. That makes
four for a single engine boat, eight for twin. The problem here
is that they all need to be inspected and serviced at least annually.
Yes, you are correct. Servicing eight coolers is expensive. But,
then, so is overhauling or replacing an engine or two. This is one
reason we posit the question of whether you can really afford diesels
or not. Many boat owners simply cannot afford this, and so run their
engines till they quit. Or put up the for sale sign when it starts
blowing smoke.
Why is this necessary?
Several reasons. You replace the zincs on your boat at least once
a year, but perhaps you weren't aware that your engine is full of
the same saltwater that your boat is floating in. If you have corrosion
problems on the hull of your boat, then you have corrosion problems
inside your engine. Not inspecting the cooling system annually (by
means of dismantling it) is like trusting the weather forecast.
Another reason is that sea strainer do not take out all foreign
material, and deposits of debris can build up inside. Or, if you
are operating in very sandy, silty water, abrasion and erosion of
the core and other components may be taking place.
Fuel System
Faults within the fuel system generally do not cause engine damage,
but it does cause damage to itself, as well as serious performance
problems. Nowadays it is rare that diesel boats don't have good
Racor or Dahl filters. But it is not rare that many boats have dirty
fuel system problems, whether the contaminated fuel results from
internal conditions, or taking contaminated fuel on board. Some
of the better fuel docks today have open filters where you can actually
see whether any contamination is being removed from the fuel. To
say the least, this is comforting.
Unfortunately, water
can accumulate in your tank. The most common way this happens --
and it's remarkable that most people never think of it -- is that
the fuel filler cap is leaking. The second most common source is
through an improperly installed vent line. The third is condensation
in the tank. In southeast Florida tank condensation is fairly rare
because temperature changes are not conducive. From the central
west coast on north it is.
People often ask us
whether they should maintain their tanks full at all times. The
answer to this is not that straightforward. It depends on how much
fuel you use. It is not wise to allow old and aging fuel to accumulate
in your tank. If you top off after short, infrequent operation every
time, the fuel in your tank is going to get old. This can foul up
your injectors. But so will water. Water causes bacterial blooms
in the fuel, and it only takes a very small amount of water to do
this. To my way of thinking, you'd be better off with this happening
to a nearly empty tank than a nearly full one. For the most part,
it's going to depend on how much of a bacteria problem you have,
and whether frequent changing of your filters can handle it.
Long winter layups present
an obvious problem. If you have one of those fuel filtering services
in your area, that is the way to go since the cost of filters and
aggravation can more than make the cost of this service worthwhile.
Plus it absolutely does the job.
Vent Filters
Many boat builders are installing vent filters on tank vent lines.
These need to be serviced, so don't forget about them or one
day an engine may magically crap out for no apparent reason.
Aspiration System
The temperature and cleanliness of the air your engine breathes
is very important. That's why most engine manufacturers are now
supplying some kind of air filtration system with their engines,
after we've complained about engines breathing salty air for years.
There's no end to the ways engines can end up breathing not only
dirty air, but air that is full of all sorts of crap like sand.
And yes, inside your boat. A typical example is on a trawler
type boat with wooden soles. The gap in the hatches is directly
over the air intake, and dirt from the sole falls right down the
gaps and into the engine. One of the most common problems is engines
sucking in crap from deteriorating carpeting backings. Yep, engines
eating carpeting, fibers and all.
If you don't have air
filters on your engines, get them installed NOW!
Turbo charged engines
usually require that the air from the hot turbo be cooled. This
is done with an inter or after cooler, take your choice of names.
Not only do these gizmos cool intake air, but they filter it too.
Not by design, but by the same means your air conditioner inadvertently
filters air. This clogs the cooler up with a corresponding rise
in engine temperature. If your cooling system is already weak, this
can be fatal. Yep, you guessed it. Here's yet another cooler to
add to the cost of the maintenance bill. You small boaters, are
you really sure you want diesel? Get out the checkbook.
Yet another problem
is air starvation. Fairly common, this is the result of improper
boat design from inadequate ventilation. It, too, causes engine
overheating. You can tell when this condition is present when, under
way, you go to lift an engine hatch or door and there is a vacuum
fighting against it. Another telltale is when you get a dark
halo around the perimeter of carpeting and carpeted hatches. This
is an absolutely sure sign that the engine room vents are
not adequate.
Cumulative Effects
The demise of most diesel engines is caused by the cumulative
effects of improper maintenance and resulting overheats. Then, suddenly
one day the engine goes bang for no apparent reason. There's a reason
all right, but it's the cumulative effect of poor maintenance. For
the most part, diesels are very unforgiving of neglect. Oh, I know
you're probably thinking about those boating books you've read that
talk about how rugged and dependable diesels are. I've seen them
too. But if you look closely, you'll see that they are not talking
about HI PERFORMANCE DIESELS. They're talking about those old 4
and 6 banger naturally aspirated engines that develop 110 hp. Ninety-nine
percent of diesel engines in power boats today can be classified
as high performance. Meaning that they are not slow, rugged and
dependable -- rather they are fragile engines that require a great
deal of care. It doesn't take much to push them over the edge.
Basic Service
Recommendation
My first recommendation,
if you are not doing most maintenance yourself, is that you establish
a relationship with a good diesel man, if that is possible. Engage
him to perform the following:
12 Month Operation
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Conduct a basic
engine survey annually. This is essentially an inspection to
search for small problems before they become big ones. The cost
to do this is not high, and is likely to save you big bucks
in the long run.
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Inspect sea water
pump impellers biannually.
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Take engine temperatures
with infrared gun annually.
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Clean intercooler
annually
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Open up and inspect
the sea water pump and check condition annually.
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Conduct cooling
system inspection and cleaning every two years.
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Change engine coolant
annually.
Seasonal Operation
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Conduct a basic
engine survey at beginning of season. This includes all gaskets,
hoses, belts and wiring.
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Inspect sea water
pump impellers annually.
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Conduct cooling
system inspection and cleaning every two years.
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Take engine temperatures
with infrared gun annually
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Clean intercooler
annually.
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Change engine oil
prior to lay up.
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Change engine coolant
every two years.
These recommendations
are not intended to supercede engine manufacturer recommendations.
General Dos
and Don'ts
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Don't start engines
without checking fluid levels.
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Do not permit engines
to sit without running them for more than 7 days. Try to operate
engines at least every 5 days. Allow engines to warm up, then
run at about 1500 RPM for about 5 minutes, then shut down.
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Properly lay up
engines that aren't going to be used for periods of greater
than 30 days. Long periods of disuse results in serious internal
engine rusting of cylinder walls and valves.
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Do not start engines
with throttles advanced. Do not race engines until they
are up to normal operating temperature. This is very damaging.
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Avoid prolonged
idling if possible. When trolling or idling for long periods,
always run the engine at cruise speed or higher on the way home
for at least 30 minutes to dislodge carbon deposits.
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Service fuel system
immediately if excessive exhaust emissions occur.
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Do not operate boat
at high speed with badly fouled bottom or when vibration occurs.
Posted
June 30, 1999
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